1. Field of the Invention
The present invention relates to a polishing pad conditioner and a chemical-mechanical polishing (CMP) apparatus, and more particularly to a polishing pad conditioner of a CMP apparatus for chemically and mechanically polishing a semiconductor substrate.
2. Description of the Related Art
Recently, in order to satisfy various requirements of consumers, semiconductor device fabrication technologies have been developed with the trend of improving degree of integration, reliability and response speed. Generally, the semiconductor device is manufactured by repeatedly performing a series of unit processes, such as film deposition process, photolithography process, etching process, ion implanting process, polishing process, cleaning process and drying process, on a semiconductor wafer. In those unit processes, the polishing process has been noticed as one of the main processes of the semiconductor manufacturing technology because it can enhance the integration degree of the semiconductor device and the structural and electrical reliability of the semiconductor device. Currently, a chemical-mechanical polishing (CMP) process is mainly employed because a semiconductor substrate can be planarized through the chemical reaction between a slurry and the film on the semiconductor, and the mechanical friction force between a polishing pad and the film on the semiconductor.
The CMP apparatus generally has a polishing pad attached to a rotating table, a polishing head that holds a semiconductor substrate and rotates the semiconductor substrate, a slurry supplying part that supplies a slurry between the polishing pad and the semiconductor substrate, and a polishing pad conditioner that improves the surface condition of the polishing pad. Additionally, a polishing end point detecting device is installed in the CMP apparatus for determining the polishing end point of the CMP process.
The slurry serves as a medium for transferring abrasive particles and chemicals from the surface of the semiconductor substrate to be polished and to the surface of the semiconductor substrate to be polished. As for the CMP process using the slurry, the polishing rate of the semiconductor substrate becomes the main parameter of the CMP process, and the polishing rate is greatly dependent on the slurry employed during the CMP process. The abrasive particles included in the slurry generally have the diameter of approximately 10 to 1,000 Å, and the abrasive particles have a hardness substantially identical to that of the semiconductor substrate, in order to accomplish the mechanical polishing.
A plurality of grooves are concentrically formed on the surface of the polishing pad attached on the rotating table in order to uniformly supply the slurry to the surface of the polishing pad, and also minute holes for receiving the slurry are formed on the surface of the polishing pad. Types of polishing pads include soft pads and hard pads. The soft pad is usually a felt pad including urethane, and the hard pad is usually a porous urethane pad.
When the semiconductor substrate is chemically and mechanically polished with the above-mentioned polishing pad and the slurry, the minute holes may be choked with polished by-products generated during the polishing process. Thus, a pad conditioning process should be simultaneously executed with the polishing process in order to perforate the minute holes choked with the polished by-products.
A polishing pad conditioner for performing a pad conditioning process is illustratively disclosed in U.S. Pat. No. 6,325,709 (issued to Nanda et al.). The polishing pad conditioner makes contact with a polishing pad, and diamond particles are attached to the convex bottom face of the polishing pad conditioner through a nickel-plating process.
In general, a conventional polishing pad conditioner includes a conditioning disc and a disc holder. Diamond particles are attached to the bottom face of the conditioning disc that contacts the polishing pad using a bonding agent or by an electroplating process. The disc holder holds the conditioning disc by a magnetic force. However, the conditioning disc may slide from the disc holder during the polishing pad conditioning process. Such a problem can be solved by combining the conditioning disc with the disc holder using bolts.
FIG. 1 is a schematic cross-sectional view illustrating a conventional polishing pad conditioner 100. Referring to FIG. 1, diamond particles 112 are attached to the bottom face of the conditioning disc 110 using an adhesive or by an electroplating process, and a plurality of screw holes are formed at the peripheral portion of the upper face of the conditioning disc 110.
The disc holder 120 has a disc shape with a diameter identical to that of the conditioning disc 110, and a plurality of penetration holes are formed at the edge peripheral portion of the disc holder 120. The bolts 130 pass through the penetration holes of the disc holder 120, and are inserted into the screw holes of the conditioning disc 110 so that the bolts 130 combine the conditioning disc 110 with the disc holder 120. The penetration holes of the disc holder 120 have stepped portions from the upper face of the disc holder 120 in order to receive the heads of the bolts.
A rotation shaft 140 is connected to the central portion of the upper face of the disc holder 120 for transmitting a rotation force, and an air bladder 150 is installed at the central portion of the rotation shaft 140 for upwardly and downwardly moving the conditioning disc 110 and the disc holder 120. A space 152 is provided in the air bladder 150 for receiving air, and the volume of the air bladder 150 is controlled in accordance with the pressure of the air received in the space 152. The conditioning disc 110 and the disc holder 120 upwardly or downwardly move according to the expansion and the contraction of the air bladder 150 due to the variation of the pressure therein.
However, the polishing pad conditioner 100 including the bolts 130 is heavier than the polishing pad conditioner that utilizes a magnetic force to hold a conditioning disc. In fact, the weight of the conditioning disc and the disc holder of the polishing pad conditioner utilizing the magnetic force are approximately 285 g and 160 g, respectively. On the other hand, the weight of the conditioning disc 110 and the disc holder 120 of the polishing pad conditioner 100 including the bolts 130 are approximately 430 g and 360 g, respectively.
Accordingly, it is difficult to control the upward and the downward motions of the heavy polishing pad conditioner 100. That is, the volume of the air bladder 150 may be difficult to control because of the heavy polishing pad conditioner 100. For example, if the air bladder 150 is exceedingly expanded, the conditioning disc 110 is too tightly contacted with the polishing pad so that the polishing pad may be damaged. On the other hand, the conditioning disc 110 does not make contact with the polishing pad if the air bladder 150 is not normally expanded. In addition, the durability and service life of the air bladder 150 may be deteriorated because of the heavy polishing pad conditioner 100.
As it is described above, when the polishing pad conditioner 100 does not normally move in the upward and the downward directions, the polishing process may not be exactly performed on the semiconductor substrate because the surface condition of the polishing pad is not improved.